x86, setup: Fix EDD3.0 data verification.

Check for nonzero path in edd_has_edd30() has no sense. First, it looks
at the wrong memory. Device path starts at offset 30 of the info->params
structure which is at offset 8 from the beginning of info structure,
but code looks at info + 4 instead. This was correct when code was
introduced, but around v2.6.4 three more fields were added to edd_info
structure (commit 66b61a5c in history.git). Second, even if it will check
correct memory it will always succeed since at offset 30 (params->key)
there will be non-zero values otherwise previous check would fail.

The patch replaces this bogus check with one that verifies checksum.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Link: http://lkml.kernel.org/r/20110426082132.GG2265@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
index 96c25d93eed1c9083bae7b8d0081c5f7255d1f95..f1b7f659d3c988d74d1453533ff75bd078c04ba9 100644 (file)
--- a/drivers/firmware/edd.c
+++ b/drivers/firmware/edd.c
@@ -531,8 +531,8 @@ static int
 edd_has_edd30(struct edd_device *edev)
 {
        struct edd_info *info;
-       int i, nonzero_path = 0;
-       char c;
+       int i;
+       u8 csum = 0;
 
        if (!edev)
                return 0;
@@ -544,16 +544,16 @@ edd_has_edd30(struct edd_device *edev)
                return 0;
        }
 
-       for (i = 30; i <= 73; i++) {
-               c = *(((uint8_t *) info) + i + 4);
-               if (c) {
-                       nonzero_path++;
-                       break;
-               }
-       }
-       if (!nonzero_path) {
+
+       /* We support only T13 spec */
+       if (info->params.device_path_info_length != 44)
+               return 0;
+
+       for (i = 30; i < info->params.device_path_info_length + 30; i++)
+               csum += *(((u8 *)&info->params) + i);
+
+       if (csum)
                return 0;
-       }
 
        return 1;
 }